Pulmonary artery pressure in thoracic scoliosis during and after exercise while breathing air and pure oxygen.

Pulmonary artery catheterisation was carried out in 25 scoliotics aged 13 to 67 years (mean 30.7). Each then performed a progressive exercise test breathing air, and 11 performed a similar test breathing pure oxygen. The mean pulmonary artery pressure (PAP) increased linearly with oxygen uptake (VO2) and with the work rate. The pressure responses have been described in terms of ther intercept and rate of rise of pressure (sPAP/VO2 and sPAP/work rate). sPAP/VO2 was unrelated to the anatomical features of the scoliosis, or to PaO2. It was inversely related to vital capacity, functional residual capacity, and total lung capacity. Inspiration of pure oxygen lowered the resting pressure by a mean of 3.2 mmHg but only decreased sPAP/work rate by 9%. The maximum pressure reached during exercise was diminished by a mean of 5.2 mmHg when pure oxygen was breathed. The mean pressures were shown to fall exponentially after exercise. The time constants were proportional to sPAP/VO2 and to the final pressure reached during exercise. Inspiration of pure oxygen did not effect the time constants but decreased the post-exercise pressure load by lowering the final pressure during exercise.